MetaFun - Pragma ADE

106
also i
fi
withcolor white-(redpart i, greenpart i, bluepart i) ;
endfor ;
pp
enddef ;
We probably need to handle a few more border cases, but for general purposes, this macro works
as expected.
From the previous examples it may be clear that each picture has some associated data stored
with it. From the bounded boolean test we can conclude that the bounding box is part of this data
Internally METAPOST keeps track of two bounding boxes: the natural one, and the forced one. The
forced one is actually a component of the picture which applies to all previously added graphics.
You can calculate the bounding box from the llcorner and urcorner or if you like ulcorner and
lrcorner and the METAFUN command boundingbox does so.
The four corners that make up the bounding box are either the natural ones, or the ones forced by
setbounds. You can force METAPOST to report the natural ones by setting truecorners to 1. The
next example demonstrates this feature.
pickup pencircle scaled 2mm ; path p, q ;
draw fullcircle
scaled 4cm slanted .5 withcolor .625white ;
setbounds currentpicture to
boundingbox currentpicture enlarged -5mm ;
interim truecorners := 0 ; p := boundingbox currentpicture ;
interim truecorners := 1 ; q := boundingbox currentpicture ;
pickup pencircle scaled 1mm ;
draw p withcolor .625red ;
draw q withcolor .625yellow ;
We use interim because truecorners is an internal METAPOST variable.
2.11 Pitfalls
When writing macros, you need to be careful in what operations apply to what object. There is for
instance a difference between the following code:
A few more details Pitfalls